Quick heat algorithm for modulating heating equipment

ABSTRACT

A system includes a modulating furnace and control circuitry. The control circuitry is configured to receive a call for heating associated with a quick heat cycle. In response to the call for heating, the control circuitry is also configured to operate the modulating furnace in a quick heat operating mode for a threshold time period. Subsequent to the threshold time period, the control circuitry is also configured to operate the modulating furnace in a modulating heat operating mode.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present disclosure andare described below. This discussion is believed to be helpful inproviding the reader with background information to facilitate a betterunderstanding of the various aspects of the present disclosure.Accordingly, it should be noted that these statements are to be read inthis light, and not as admissions of prior art.

Heating, ventilation, and/or air conditioning (HVAC) systems areutilized in residential, commercial, and industrial environments tocontrol environmental properties, such as temperature and humidity, foroccupants of the respective environments (e.g., enclosed spaces). Forexample, an HVAC system may include one or more heat exchangersconfigured to place an air flow in a heat exchange relationship with aworking fluid circulated by the heat exchanger. For example, a heatexchanger may circulate a refrigerant of a vapor compression circuit,combustion products generated by a furnace, or another type of workingfluid. In general, the heat exchange relationship(s) may cause a changein pressures and/or temperatures of the air flow, the working fluid, orboth. After exchanging heat via the heat exchanger, the air flow may bedirected toward the environment (e.g., enclosed space) to condition theenvironment. Control features may be employed to control theabove-described features such that conditions of the environment areadjusted in a desired manner. Unfortunately, traditional HVAC systemsmay be ill-equipped to determine whether, how, and/or when to operateheat exchangers to quickly and/or efficiently provide conditioning tothe environment (e.g., enclosed space), which may result in inefficientheat exchange and/or extended amounts of time to condition theenvironment and satisfy a call for conditioning. Accordingly, it is nowrecognized that improved operation of heat exchangers is desired.

SUMMARY

A summary of certain embodiments disclosed herein is set forth below. Itshould be noted that these aspects are presented merely to provide thereader with a brief summary of these certain embodiments and that theseaspects are not intended to limit the scope of this disclosure. Indeed,this disclosure may encompass a variety of aspects that may not be setforth below.

In an embodiment, a controller of a modulating furnace of a heating,ventilation, and air conditioning (HVAC) system includes a tangible,non-transitory, computer-readable medium having computer-executableinstructions stored thereon that, when executed, are configured to causeprocessing circuitry to receive a call for heating and associate thecall for heating with a quick heat cycle. The instructions storedthereon, that when executed, are configured to cause the processingcircuitry to also operate the modulating furnace in a quick heatoperating mode for a threshold time period in response to the call forheating being associated with the quick heat cycle and operate themodulating furnace in a modulating heat operating mode subsequent toexpiration of the threshold time period.

A heating, ventilation, and air conditioning (HVAC) system includes amodulating furnace and control circuitry configured to receive a callfor heating associated with a quick heat cycle. In response to the callfor heating, the control circuitry is configured to operate themodulating furnace in a quick heat operating mode for a threshold timeperiod and subsequent to the threshold time period, operate themodulating furnace in a modulating heat operating mode.

A heating, ventilation, and air conditioning (HVAC) system includes amodulating furnace and a processor configured to receive a call from athermostat. In response to the call, the processor is configured toexecute a quick heat algorithm to determine a number of heating cyclesbetween the call and a previous call associated with the quick heatalgorithm and compare the number of heating cycles to a threshold cycleamount. In response to the number of heating cycles meeting or exceedingthe threshold cycle amount, the processor is configured to execute thequick heat algorithm to also initiate operation of the modulatingfurnace and operate the modulating furnace in a quick heat operatingmode. In response to the number of heating cycles being below thethreshold cycle amount, the processor is configured to execute the quickheat algorithm to operate the modulating furnace in a modulating heatoperating mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of this disclosure may be better understood upon readingthe following detailed description and upon reference to the drawings inwhich:

FIG. 1 is a perspective view of a building having an embodiment of aheating, ventilation, and/or air conditioning (HVAC) system forenvironmental management that may employ one or more HVAC units, inaccordance with an aspect of the present disclosure;

FIG. 2 is a perspective view of an embodiment of a packaged HVAC unitthat may be used in an HVAC system, in accordance with an aspect of thepresent disclosure;

FIG. 3 is a cutaway perspective view of an embodiment of a residential,split HVAC system, in accordance with an aspect of the presentdisclosure;

FIG. 4 is a schematic illustration of an embodiment of a vaporcompression system that can be used in any of the systems of FIGS. 1-3 ,in accordance with an aspect of the present disclosure;

FIG. 5 is a schematic diagram of an embodiment of a modulating furnaceconfigured to provide improved conditioning for a conditioned space, inaccordance with an aspect of the present disclosure;

FIG. 6 is a perspective view of an embodiment of a modulating furnaceconfigured to provide improved conditioning for a conditioned space, inaccordance with an aspect of the present disclosure;

FIG. 7 is a schematic diagram of an embodiment of a control system for amodulating furnace, in accordance with an aspect of the presentdisclosure;

FIG. 8 is a process flow diagram illustrating an embodiment of a methodof executing a quick heat algorithm of a modulating furnace, inaccordance with an aspect of the present disclosure;

FIG. 9 is a block diagram of an embodiment of a sequence of cycles for amodulating furnace, in accordance with an aspect of the presentdisclosure; and

FIG. 10 is a process flow diagram illustrating an embodiment of a methodof executing a quick heat algorithm of a modulating furnace based on anumber of completed cycles, in accordance with an aspect of the presentdisclosure.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effortto provide a concise description of these embodiments, not all featuresof an actual implementation are described in the specification. Itshould be noted that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be noted that such a development effortmight be complex and time consuming, but would nevertheless be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the presentdisclosure, the articles “a,” “an,” and “the” are intended to mean thatthere are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements.Additionally, it should be noted that references to “one embodiment” or“an embodiment” of the present disclosure are not intended to beinterpreted as excluding the existence of additional embodiments thatalso incorporate the recited features.

The present disclosure is directed to systems and methods for improvingoperation of heat exchangers of HVAC systems. More particularly, presentembodiments include systems and methods for operating a heat exchanger(e.g., a modulating furnace) in multiple operating modes, including aquick heat operating mode or cycle. As used herein, a “quick heat cycle”refers to an operating mode for a modulating furnace in which one ormore operating parameters of the modulating furnace is at an upperthreshold (e.g., upper threshold value) and/or the modulating furnace isoperated at a full (e.g., predefined maximum heating, maximum, 100percent) capacity. For example, in the quick heat cycle, a fuel inputrate to burner(s) of the modulating furnace may be at an upper threshold(e.g., maximum) value and/or an exhaust flow rate of a blower of themodulating furnace may be at an upper threshold (e.g., maximum) value.Additionally or alternatively, the predefined maximum heating capacitymay be a selected (e.g., based on a user input received via a userinterface) limit of the heating capacity of the modulating furnace. Themodulating furnace may also be operated in a modulating heat mode orcycle. As used herein, a “modulating heat cycle” refers to an operatingmode for a modulating furnace during which a capacity (e.g., heatoutput, rate of heat transfer, etc.) of the modulating furnace ismodulated or varied. For example, in the modulating heat cycle, a fuelinput rate to burner(s) of the modulating furnace and/or an exhaust flowrate of a blower of the modulating furnace may be adjusted or modulated,such as based on feedback and/or control signals from a controller ofthe HVAC system. In some embodiments, the feedback may include atemperature difference between a set point temperature and a measured(e.g., current) temperature in an environment (e.g., enclosed space)conditioned by the modulating furnace. As discussed below, presentembodiments also include systems and methods to determining whether,how, and when to initiate the various operating modes of the modulatingfurnace.

A modulating furnace, such as a variable speed furnace, is configured toadjust an amount of heat output and/or temperature of heated airgenerated by the modulating furnace to provide heating to a conditionedspace at a faster rate and/or more efficiently than traditional (e.g.,fixed rate) furnaces. The modulating furnace may include one or moreburners configured to receive fuel (e.g., gas) from a fuel source. Afuel valve (e.g., gas valve) associated with the modulating furnace maybe controlled to supply a variable amount of fuel to the burner. Inaccordance with present embodiments, an amount and/or rate of fuelsupplied to the burner may be based on an operating mode (e.g., aselected operating mode) of the modulating furnace. For example, thefuel valve may be adjusted to increase a fuel input rate to themodulating furnace during a quick heat cycle of the modulating furnace.The burners may also receive an oxidant (e.g., air), mix the oxidantwith the fuel, and ignite the fuel-oxidant mixture to generatecombustion products routed through heat exchange tubes or coils of themodulating furnace. The modulating furnace may also include one or moreblowers (e.g., draft inducer blowers) configured to draw exhaust gas(e.g., combustion products) through the heat exchange tubes of themodulating furnace. For example, a blower associated with the modulatingfurnace may be controlled to generate a varying flow rate of the exhaustgas through the heat exchange tubes. In some embodiments, during thequick heat cycle, the blower may be adjusted to increase a flow rate ofthe exhaust gas through the heat exchange tubes. To enable the featuresdescribed herein, the modulating furnace and/or the HVAC system mayinclude a control system (e.g., a controller) to regulate operation ofthe modulating furnace (e.g., the fuel valve, the blower, etc.).

In accordance with present embodiments, a controller of the HVAC systemand/or modulating furnace may receive a call (e.g., from a thermostat)to provide conditioning (e.g., heating) to a space conditioned by theHVAC system. The controller may include a processor and a memory, andthe memory may include instructions stored thereon that, when executedby the processor, cause the controller to selectively execute one of thevarious operating modes of the modulating furnace. For example,instructions may include a quick heat algorithm. In the manner describedbelow, the controller may execute the quick heat algorithm and, based onan output from the quick heat algorithm, initiate operation of themodulating furnace in the quick heat operating mode for a threshold timeperiod. After the threshold time period, the controller may operate themodulating furnace in the modulating heat operating mode (e.g., if thecall for conditioning remains after operation of the modulating furnacein the quick heat operating mode).

The quick heat algorithm may initiate operation of the quick heatoperating mode based on various inputs, calculations, and/or factors.For example, the quick heat algorithm may initiate the quick heatoperating mode based on a user input. The quick heat algorithm may alsoinitiate the quick heat operating mode based on whether the quick heatoperating mode was initiated in recent cycles of the modulating furnace.For example, the quick heat algorithm may determine a number ofoperating cycles completed (e.g., operating cycles executed to satisfyrespective calls for conditioning) since execution of the last quickheat cycle. The quick heat algorithm may initiate the quick heat cyclebased on a determination that the number of operating cycles completedwithout implementing the quick heat cycle meets or exceeds a thresholdnumber or value. In general, the above-described quick heat algorithmimproves heat exchange efficiency and/or reduces conditioning timerelative to traditional systems. The improvements and benefits of thedisclosed techniques is described in further detail below.

Turning now to the drawings, FIG. 1 illustrates an embodiment of aheating, ventilation, and/or air conditioning (HVAC) system forenvironmental management that may employ one or more HVAC units. As usedherein, an HVAC system includes any number of components configured toenable regulation of parameters related to climate characteristics, suchas temperature, humidity, air flow, pressure, air quality, and so forth.For example, an “HVAC system” as used herein is defined asconventionally understood and as further described herein. Components orparts of an “HVAC system” may include, but are not limited to, all, someof, or individual parts such as a heat exchanger, a heater, an air flowcontrol device, such as a fan, a sensor configured to detect a climatecharacteristic or operating parameter, a filter, a control deviceconfigured to regulate operation of an HVAC system component, acomponent configured to enable regulation of climate characteristics, ora combination thereof. An “HVAC system” is a system configured toprovide such functions as heating, cooling, ventilation,dehumidification, pressurization, refrigeration, filtration, or anycombination thereof. The embodiments described herein may be utilized ina variety of applications to control climate characteristics, such asresidential, commercial, industrial, transportation, or otherapplications where climate control is desired.

In the illustrated embodiment, a building 10 is air conditioned by asystem that includes an HVAC unit 12. The building 10 may be acommercial structure or a residential structure. As shown, the HVAC unit12 is disposed on the roof of the building 10; however, the HVAC unit 12may be located in other equipment rooms or areas adjacent the building10. The HVAC unit 12 may be a single package unit containing otherequipment, such as a blower, integrated air handler, and/or auxiliaryheating unit. In other embodiments, the HVAC unit 12 may be part of asplit HVAC system, such as the system shown in FIG. 3 , which includesan outdoor HVAC unit 58 and an indoor HVAC unit 56.

The HVAC unit 12 is an air cooled device that implements a refrigerationloop to provide conditioned air to the building 10. Specifically, theHVAC unit 12 may include one or more heat exchangers across which an airflow is passed to condition the air flow before the air flow is suppliedto the building. In the illustrated embodiment, the HVAC unit 12 is arooftop unit (RTU) that conditions a supply air stream, such asenvironmental air and/or a return air flow from the building 10. Afterthe HVAC unit 12 conditions the air, the air is supplied to the building10 via ductwork 14 extending throughout the building 10 from the HVACunit 12. For example, the ductwork 14 may extend to various individualfloors or other sections of the building 10. In certain embodiments, theHVAC unit 12 may be a heat pump that provides both heating and coolingto the building with one refrigeration circuit configured to operate indifferent modes. In other embodiments, the HVAC unit 12 may include oneor more refrigeration circuits for cooling an air stream and a furnacefor heating the air stream.

A control device 16, one type of which may be a thermostat, may be usedto designate the temperature of the conditioned air. The control device16 also may be used to control the flow of air through the ductwork 14.For example, the control device 16 may be used to regulate operation ofone or more components of the HVAC unit 12 or other components, such asdampers and fans, within the building 10 that may control flow of airthrough and/or from the ductwork 14. In some embodiments, other devicesmay be included in the system, such as pressure and/or temperaturetransducers or switches that sense the temperatures and pressures of thesupply air, return air, and so forth. Moreover, the control device 16may include computer systems that are integrated with or separate fromother building control or monitoring systems, and even systems that areremote from the building 10.

FIG. 2 is a perspective view of an embodiment of the HVAC unit 12. Inthe illustrated embodiment, the HVAC unit 12 is a single package unitthat may include one or more independent refrigeration circuits andcomponents that are tested, charged, wired, piped, and ready forinstallation. The HVAC unit 12 may provide a variety of heating and/orcooling functions, such as cooling only, heating only, cooling withelectric heat, cooling with dehumidification, cooling with gas heat, orcooling with a heat pump. As described above, the HVAC unit 12 maydirectly cool and/or heat an air stream provided to the building 10 tocondition a space in the building 10.

As shown in the illustrated embodiment of FIG. 2 , a cabinet 24 enclosesthe HVAC unit 12 and provides structural support and protection to theinternal components from environmental and other contaminants. In someembodiments, the cabinet 24 may be constructed of galvanized steel andinsulated with aluminum foil faced insulation. Rails 26 may be joined tothe bottom perimeter of the cabinet 24 and provide a foundation for theHVAC unit 12. In certain embodiments, the rails 26 may provide accessfor a forklift and/or overhead rigging to facilitate installation and/orremoval of the HVAC unit 12. In some embodiments, the rails 26 may fitonto “curbs” on the roof to enable the HVAC unit 12 to provide air tothe ductwork 14 from the bottom of the HVAC unit 12 while blockingelements such as rain from leaking into the building 10.

The HVAC unit 12 includes heat exchangers 28 and 30 in fluidcommunication with one or more refrigeration circuits. Tubes within theheat exchangers 28 and 30 may circulate refrigerant, such as R-410A,through the heat exchangers 28 and 30. The tubes may be of varioustypes, such as multichannel tubes, conventional copper or aluminumtubing, and so forth. Together, the heat exchangers 28 and 30 mayimplement a thermal loop in which the refrigerant undergoes phasechanges and/or temperature changes as it flows through the heatexchangers 28 and 30 to produce heated and/or cooled air. For example,the heat exchanger 28 may function as a condenser where heat is releasedfrom the refrigerant to ambient air, and the heat exchanger 30 mayfunction as an evaporator where the refrigerant absorbs heat to cool anair stream. In other embodiments, the HVAC unit 12 may operate in a heatpump mode where the roles of the heat exchangers 28 and 30 may bereversed. That is, the heat exchanger 28 may function as an evaporatorand the heat exchanger 30 may function as a condenser. In furtherembodiments, the HVAC unit 12 may include a furnace for heating the airstream that is supplied to the building 10. While the illustratedembodiment of FIG. 2 shows the HVAC unit 12 having two of the heatexchangers 28 and 30, in other embodiments, the HVAC unit 12 may includeone heat exchanger or more than two heat exchangers.

The heat exchanger 30 is located within a compartment 31 that separatesthe heat exchanger 30 from the heat exchanger 28. Fans 32 draw air fromthe environment through the heat exchanger 28. Air may be heated and/orcooled as the air flows through the heat exchanger 28 before beingreleased back to the environment surrounding the HVAC unit 12. A blowerassembly 34, powered by a motor 36, draws air through the heat exchanger30 to heat or cool the air. The heated or cooled air may be directed tothe building 10 by the ductwork 14, which may be connected to the HVACunit 12. Before flowing through the heat exchanger 30, the conditionedair flows through one or more filters 38 that may remove particulatesand contaminants from the air. In certain embodiments, the filters 38may be disposed on the air intake side of the heat exchanger 30 toprevent contaminants from contacting the heat exchanger 30.

The HVAC unit 12 also may include other equipment for implementing thethermal loop. Compressors 42 increase the pressure and temperature ofthe refrigerant before the refrigerant enters the heat exchanger 28. Thecompressors 42 may be any suitable type of compressors, such as scrollcompressors, rotary compressors, screw compressors, or reciprocatingcompressors. In some embodiments, the compressors 42 may include a pairof hermetic direct drive compressors arranged in a dual stageconfiguration 44. However, in other embodiments, any number of thecompressors 42 may be provided to achieve various stages of heatingand/or cooling. Additional equipment and devices may be included in theHVAC unit 12, such as a solid-core filter drier, a drain pan, adisconnect switch, an economizer, pressure switches, phase monitors, andhumidity sensors, among other things.

The HVAC unit 12 may receive power through a terminal block 46. Forexample, a high voltage power source may be connected to the terminalblock 46 to power the equipment. The operation of the HVAC unit 12 maybe governed or regulated by a control board 48. The control board 48 mayinclude control circuitry connected to a thermostat, sensors, andalarms. One or more of these components may be referred to hereinseparately or collectively as the control device 16. The controlcircuitry may be configured to control operation of the equipment,provide alarms, and monitor safety switches. Wiring 49 may connect thecontrol board 48 and the terminal block 46 to the equipment of the HVACunit 12.

FIG. 3 illustrates a residential heating and cooling system 50, also inaccordance with present techniques. The residential heating and coolingsystem 50 may provide heated and cooled air to a residential structure,as well as provide outside air for ventilation and provide improvedindoor air quality (IAQ) through devices such as ultraviolet lights andair filters. In the illustrated embodiment, the residential heating andcooling system 50 is a split HVAC system. In general, a residence 52conditioned by a split HVAC system may include refrigerant conduits 54that operatively couple the indoor unit 56 to the outdoor unit 58. Theindoor unit 56 may be positioned in a utility room, an attic, abasement, and so forth. The outdoor unit 58 is typically situatedadjacent to a side of residence 52 and is covered by a shroud to protectthe system components and to prevent leaves and other debris orcontaminants from entering the unit. The refrigerant conduits 54transfer refrigerant between the indoor unit 56 and the outdoor unit 58,typically transferring primarily liquid refrigerant in one direction andprimarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 3 is operating as an air conditioner, aheat exchanger 60 in the outdoor unit 58 serves as a condenser forre-condensing vaporized refrigerant flowing from the indoor unit 56 tothe outdoor unit 58 via one of the refrigerant conduits 54. In theseapplications, a heat exchanger 62 of the indoor unit functions as anevaporator. Specifically, the heat exchanger 62 receives liquidrefrigerant, which may be expanded by an expansion device, andevaporates the refrigerant before returning it to the outdoor unit 58.

The outdoor unit 58 draws environmental air through the heat exchanger60 using a fan 64 and expels the air above the outdoor unit 58. Whenoperating as an air conditioner, the air is heated by the heat exchanger60 within the outdoor unit 58 and exits the unit at a temperature higherthan it entered. The indoor unit 56 includes a blower or fan 66 thatdirects air through or across the indoor heat exchanger 62, where theair is cooled when the system is operating in air conditioning mode.Thereafter, the air is passed through ductwork 68 that directs the airto the residence 52. The overall system operates to maintain a desiredtemperature as set by a system controller. When the temperature sensedinside the residence 52 is higher than the set point on the thermostat,or the set point plus a small amount, the residential heating andcooling system 50 may become operative to refrigerate additional air forcirculation through the residence 52. When the temperature reaches theset point, or the set point minus a small amount, the residentialheating and cooling system 50 may stop the refrigeration looptemporarily.

The residential heating and cooling system 50 may also operate as a heatpump. When operating as a heat pump, the roles of heat exchangers 60 and62 are reversed. That is, the heat exchanger 60 of the outdoor unit 58will serve as an evaporator to evaporate refrigerant and thereby coolair entering the outdoor unit 58 as the air passes over the outdoor heatexchanger 60. The indoor heat exchanger 62 will receive a stream of airblown over it and will heat the air by condensing the refrigerant.

In some embodiments, the indoor unit 56 may include a furnace system 70.For example, the indoor unit 56 may include the furnace system 70 whenthe residential heating and cooling system 50 is not configured tooperate as a heat pump. The furnace system 70 may include a burnerassembly and heat exchanger, among other components, inside the indoorunit 56. Fuel is provided to the burner assembly of the furnace system70 where it is mixed with air and combusted to form combustion products.The combustion products may pass through tubes or piping in a heatexchanger, separate from heat exchanger 62, such that air directed bythe blower or fan 66 passes over the tubes or pipes and extracts heatfrom the combustion products. The heated air may then be routed from thefurnace system 70 to the ductwork 68 for heating the residence 52.

FIG. 4 is an embodiment of a vapor compression system 72 that can beused in any of the systems described above. The vapor compression system72 may circulate a refrigerant through a circuit starting with acompressor 74. The circuit may also include a condenser 76, an expansionvalve(s) or device(s) 78, and an evaporator 80. The vapor compressionsystem 72 may further include a control panel 82 that has an analog todigital (A/D) converter 84, a microprocessor 86, a non-volatile memory88, and/or an interface board 90. The control panel 82 and itscomponents may function to regulate operation of the vapor compressionsystem 72 based on feedback from an operator, from sensors of the vaporcompression system 72 that detect operating conditions, and so forth.

In some embodiments, the vapor compression system 72 may use one or moreof a variable speed drive (VSDs) 92, a motor 94, the compressor 74, thecondenser 76, the expansion valve or device 78, and/or the evaporator80. The motor 94 may drive the compressor 74 and may be powered by thevariable speed drive (VSD) 92. The VSD 92 receives alternating current(AC) power having a particular fixed line voltage and fixed linefrequency from an AC power source, and provides power having a variablevoltage and frequency to the motor 94. In other embodiments, the motor94 may be powered directly from an AC or direct current (DC) powersource. The motor 94 may include any type of electric motor that can bepowered by a VSD or directly from an AC or DC power source, such as aswitched reluctance motor, an induction motor, an electronicallycommutated permanent magnet motor, or another suitable motor.

The compressor 74 compresses a refrigerant vapor and delivers the vaporto the condenser 76 through a discharge passage. In some embodiments,the compressor 74 may be a centrifugal compressor. The refrigerant vapordelivered by the compressor 74 to the condenser 76 may transfer heat toa fluid passing across the condenser 76, such as ambient orenvironmental air 96. The refrigerant vapor may condense to arefrigerant liquid in the condenser 76 as a result of thermal heattransfer with the environmental air 96. The liquid refrigerant from thecondenser 76 may flow through the expansion device 78 to the evaporator80.

The liquid refrigerant delivered to the evaporator 80 may absorb heatfrom another air stream, such as a supply air stream 98 provided to thebuilding 10 or the residence 52. For example, the supply air stream 98may include ambient or environmental air, return air from a building, ora combination of the two. The liquid refrigerant in the evaporator 80may undergo a phase change from the liquid refrigerant to a refrigerantvapor. In this manner, the evaporator 80 may reduce the temperature ofthe supply air stream 98 via thermal heat transfer with the refrigerant.Thereafter, the vapor refrigerant exits the evaporator 80 and returns tothe compressor 74 by a suction line to complete the loop.

In some embodiments, the vapor compression system 72 may further includea reheat coil in addition to the evaporator 80. For example, the reheatcoil may be positioned downstream of the evaporator relative to thesupply air stream 98 and may reheat the supply air stream 98 when thesupply air stream 98 is overcooled to remove humidity from the supplyair stream 98 before the supply air stream 98 is directed to thebuilding 10 or the residence 52.

Any of the features described herein may be incorporated with the HVACunit 12, the residential heating and cooling system 50, or other HVACsystems. Additionally, while the features disclosed herein are describedin the context of embodiments that directly heat and cool a supply airstream provided to a building or other load, embodiments of the presentdisclosure may be applicable to other HVAC systems as well. For example,the features described herein may be applied to mechanical coolingsystems, free cooling systems, chiller systems, or other heat pump orrefrigeration applications.

Further, any of the systems illustrated in FIGS. 1-4 may include afurnace, such as a modulating furnace, and a controller configured toimplement a quick heat algorithm that enables improved operation of themodulating furnace. For example, the quick heat algorithm is configuredto determine whether, how, and/or when to initiate a quick heat cycleoperation of the modulating furnace. As previously described, amodulating furnace, such as a variable speed furnace, is configured toadjust an amount of heat output by the modulating furnace and/ortemperature of heated air generated by the modulating furnace. In thisway, the modulating furnace is configured to provide conditioning (e.g.,heating) to a conditioned space more quickly and/or more efficientlythan traditional furnaces. While modulating furnaces are described indetail below, it should be understood that the quick heat algorithm andtechniques described in in the present disclosure may also be utilizedwith modulating cooling systems, such as a refrigerant-based evaporatorconfigured to absorb heat from an air flow, modulating heating systemsincluding additional or other components than those described herein,such as an electric heater, modulating dehumidification systems, orother variable conditioning systems.

FIG. 5 is a schematic diagram of an embodiment of an HVAC system 100including a modulating furnace 104 and a furnace control system 106operatively coupled to the modulating furnace 104. The modulatingfurnace 104 and/or furnace control system 106 may implemented in any ofthe systems or units illustrated in FIGS. 1-4 . The furnace controlsystem 106 is configured to regulate operation of components of themodulating furnace 104 to generate a conditioned (e.g., heated) air flowto be supplied to an interior space 119 (e.g., a space within thebuilding 10). The modulating furnace 104 includes an air blower 108, aheat exchanger 110, and a burner assembly 116 that operate to heat air118 received by the modulating furnace 104 before directing the airtowards the interior space 119. As illustrated, one or more componentsof the modulating furnace 104 may be disposed within an enclosure 120that receives the air 118 and directs the air 118 across and/or over theheat exchanger 110. However, in some embodiments, the heat exchanger110, the burner assembly 116, and other components of the modulatingfurnace 104 may be housed in separate enclosures, separate portions ofthe enclosure 120, or in a shared portion of the enclosure 120.Moreover, although schematically illustrated in FIG. 5 as having oneheat exchanger 110, any suitable number of heat exchangers, includingprimary and secondary heat exchangers of a condensing furnace system,may be used within the modulating furnace 104 for transferring heat tothe air 118.

As shown, the modulating furnace 104 includes a fuel source 122 toprovide a fuel 124 to burners 126 of the burner assembly 116. The fuel124 may include natural gas, liquified petroleum gas, fuel oil, coal, oranother suitable fuel. The burners 126 ignite the fuel 124 to generatethermal energy (e.g., combustion products, exhaust gas, etc.) fortransfer to the air 118 via the heat exchanger 110, as discussed in moredetail below. The burners 126 may include any suitable body, nozzle, ortube having an inlet for receiving the fuel 124 and an outlet fordirecting the fuel 124 therefrom. As illustrated, a modulating gas valve128 or gas regulation device is fluidly coupled between the fuel source122 and the burner assembly 116 to regulate a fuel input rate of thefuel 124 provided to the burners 126 of the burner assembly 116.Although described herein with reference to the modulating gas valve128, it is to be understood that the modulating furnace 104 mayadditionally or alternatively include any suitable gas regulation deviceor system, such as a pressure regulator, configured to regulate flow ofthe fuel 124. Additionally, in some embodiments, an oxidant orcombustion air source 132 may provide combustion air 134 or some otheroxidant to the burners 126 of the burner assembly 116. For example, thecombustion air 134 may be drawn into each individual burner 126 of theburner assembly 116 to mix with the fuel 124 drawn into each individualburner 126 of the burner assembly 116. In some embodiments, thecombustion air source 132 may be an area within the burner assembly 116external to the individual burners 126 of the burner assembly 116.

The combustion air 134 may mix with the fuel 124 in the burners 126and/or adjacent to the burners 126 to form a combustible mixture, whichmay be referred to herein as an air-fuel mixture. The air-fuel mixturemay be ignited via an igniter 144 coupled to the burner assembly 116.For example, a pulse (e.g., control signal) may be sent through theigniter 144 to instruct the igniter 144 to produce a spark adjacent orwithin the burners 126 of the burner assembly 116. In some embodiments,the air-fuel mixture is ignited in one ignitable burner 146 proximatethe igniter 144, which sequentially ignites the air-fuel mixture inadjacent burners 126. In other embodiments, the air-fuel mixture may beignited by other components or elements, such as hot surface igniter ora pilot light flame. In the illustrated embodiment, once ignited, theair-fuel mixture drawn through the burners 126 of the burner assembly116 may form combustion products, such as a hot exhaust gas 148. Thefurnace control system 106 may control operation of the components ofthe modulating furnace 104 to maintain robust flames, such as flamesextending outside of bodies of the burners 126. In this way, the burnerassembly 116 may produce the hot exhaust gas 148 at a desiredtemperature, composition, and/or efficiency. The hot exhaust gas 148 maybe directed through the heat exchanger 110 (e.g., through tubes of theheat exchanger 110) to enable heat transfer from the hot exhaust gas 148to the air 118.

Further, the furnace control system 106 may include a flame sensor 150coupled to the burner assembly 116 to sense or detect a presence of aflame on a sensed burner 152, opposed from the ignitable burner 146(e.g., relative to other burners 126 of the burner assembly 116). Assuch, the flame sensor 150 enables the furnace control system 106 toverify whether the air-fuel mixture within each of the burners 126 hasbeen ignited.

The modulating furnace 104 may also include a draft inducer blower 154fluidly coupled to a distal portion 156 of the heat exchanger 110 (e.g.,heat exchange tubes), opposite a proximal portion 158 of the heatexchanger 110 that is proximate the burner assembly 116. In certainembodiments, the combustion air 134 may be drawn into the burners 126 ofthe burner assembly 116 at least partially due to a pressure differencegenerated by the draft inducer blower 154, which may also operate todraw the hot exhaust gas 148 through the heat exchanger 110. In otherwords, a flow path for the combustion air 134 and the hot exhaust gas148 extends from the burners 126 of the burner assembly 116 to the draftinducer blower 154. Thus, the draft inducer blower 154 may operate todraw both the combustion air 134 into the burners 126 of the burnerassembly 116 and the hot exhaust gas 148 through the flow path betweenthe draft inducer blower 154 and the burner assembly 116. Additionally,as the draft inducer blower 154 draws the hot exhaust gas 148 throughthe heat exchanger 110, the hot exhaust gas 148 may cool into exhaustgas 160, which the draft inducer blower 154 may direct into an exhauststack 164 of the modulating furnace 104. The exhaust stack 164 maydischarge the exhaust gas 160 from the modulating furnace 104 into anexternal environment 166 external to the modulating furnace 104.

Moreover, during operation of the modulating furnace 104, as the hotexhaust gas 148 is drawn through the heat exchanger 110, the air blower108 draws the air 118 into the enclosure 120 of the modulating furnace104. The air 118 is directed across coils or tubes of the heat exchanger110 to enable transfer thermal energy from the hot exhaust gas 148flowing therein to the air 118, thereby generating heated air 168. Then,the heated air 168 is discharged from the enclosure 120 and directedtoward the interior space 119. For example, the modulating furnace 104and/or HVAC system 100 may direct the heated air 168 into an airdistribution system of the building 10, such as the ducts 14 of FIG. 1 .

Further, in some embodiments, such as embodiments in which the enclosure120 of the modulating furnace 104 is configured to be disposed outsideof the building 10, the furnace control system 106 may include a windsensor 170 disposed within the external environment 166 (e.g., coupledto an external surface 172 of the enclosure 120). The wind sensor 170may be a pressure switch or any other suitable sensor configured tomonitor a presence of a wind condition and/or a wind speed and transmitsensor signals indicative of the wind condition and/or the wind speed tothe furnace control system 106. As such, the furnace control system 106may adjust control parameters based on detection of the wind condition.

Additionally, the modulating furnace 104 may be a variable speed furnacesystem configured to adjust an amount and/or rate of heat produced andtransferred to the air 118 to generate the heated air 168 provided tothe building 10. For example, based on a heat demand of the interiorspace 119 of the building 10, the modulating furnace 104 may adjust afuel input rate of the fuel 124 provided to the burners 126 to modifythe heat generated via the hot exhaust gas 148. Additionally oralternatively, in some embodiments, the draft inducer blower 154 may becontrolled to modify the flow rate of the hot exhaust gas 148 drawnthrough the heat exchanger 110 to thereby control rate of heat transferfrom the hot exhaust gas 148 to the air 118. In some embodiments, themodulating furnace 104 may alternatively be a two stage or multiplestage furnace system configured to operate at two or more different heatoutput levels or capacities, such as a low heat output level and a highheat output level.

The furnace control system 106 may further include a controller 180(e.g., control circuitry) configured to control the modulating furnace104 by transmitting control signals to various components therein. Thecontroller 180 may include a processor 182 and a memory 184 (e.g.,non-transitory, computer-readable media having instructions storedthereon. The memory 184 may include instructions stored thereon that,when executed by the processor 182, cause the controller 180 to performvarious functions (e.g., execute a quick heat algorithm in accordancewith the present disclosure). For example, the controller 180 may becommunicatively coupled to the modulating gas valve 128 and the draftinducer blower 154. As such, the controller 180 may instruct themodulating gas valve 128 to adjust a fuel input rate of the fuel 124provided to the burner assembly 116, thereby adjusting a temperature ofthe hot exhaust gas 148 produced by the burner assembly 116. Forexample, increasing the fuel input rate of fuel 124 directed into theburner assembly 116 may increase the temperature of the hot exhaust gas148 and increase the temperature of the heated air 168.

Additionally, the controller 180 may instruct the draft inducer blower154 to generate an increased flow rate of hot exhaust gas 148 throughthe heat exchanger 110. For example, the controller 180 may instruct thedraft inducer blower 154 to increase the flow rate of hot exhaust gas148 in conjunction with instructing the modulating gas valve 128 toincrease a fuel input rate of the fuel 124. Increasing the fuel inputrate of fuel 124 supplied to the burner assembly 116 and/or andincreasing the speed of the draft inducer blower 154 may be referred toas “ramping up” the modulating furnace 104 to increase an amount of heattransferred to the air 118 and provided to the interior space 119 of thebuilding 10 via the heated air 168. Conversely, decreasing the fuelinput rate and decreasing the speed of the draft inducer blower 154 maybe referred to as “ramping down” the modulating furnace 104 to reduce anamount of heat transferred to the air 118 and provided to the interiorspace 119 of the building 10 via the heated air 168. Further, in someembodiments, the controller 180 is communicatively coupled to the airblower 108 and is configured to transmit control signals to cause theair blower 108 to modify a flow rate of the air 118 across coils ortubes of the heat exchanger 110. In this way, the modulating furnace 104may adjust an amount of time the air 118 is in contact with the heatexchanger 110, for example, while ramping up or ramping down themodulating furnace 104.

FIG. 6 is a perspective view of an embodiment of the modulating furnace104. In the illustrated embodiment, the burner assembly 116 is locatednear a base 200 (e.g., a base surface) of the modulating furnace 104,and the burner assembly 116 includes multiple burners 126. As previouslydescribed, each burner 126 is configured to combust a mixture ofcombustion air 134 and fuel 124. The combustion air 134 may be drawninto each burner 126 at least partially due to a pressure differencegenerated by the draft inducer blower 154 and/or at least partially dueto air entrainment within a jet or stream of fuel 124 provided to eachburner 126 of the burner assembly 116. The fuel 124 may be provided fromthe fuel source 122 to a gas inlet 204 of the modulating gas valve 128.The modulating gas valve 128 is fluidly coupled to a manifold 206, whichdistributes the fuel 124 to a body 208 of each burner 126. In someembodiments, the fuel 124 may be evenly or substantially evenlydistributed via the manifold 206 to each burner 126. As such, themodulating gas valve 128 may control a fuel input rate to the burners126. In this way, the modulating gas valve 128 controls a quantity orvolume of the fuel 124 in the mixture of each burner 126.

Moreover, the draft inducer blower 154 is disposed on (e.g., mountedand/or attached to) an outer surface 210 of the enclosure 120 of themodulating furnace 104. As previously described, the draft inducerblower 154 draws the hot exhaust gas 148 produced at the burners 126through the heat exchanger 110 (e.g., tubes of the heat exchanger 110)within the enclosure 120. Additionally, the air blower 108 may bedisposed within the enclosure 120, for example, near the base 200 of theenclosure 120. However, in other embodiments, the air blower 108 may bedisposed external to the enclosure 120. During operation of themodulating furnace 104, the air blower 108 forces or draws the air 118over tubes of the heat exchanger 110, and heat is transferred from thehot exhaust gas 148 to the air 118. Thereafter, the heated air 168 maybe discharged from the enclosure 120 and into a duct 214, which maydirect the heated air 168 toward the interior space 119. As discussedabove, the exhaust gas 160 may be drawn from the tubes of the heatexchanger 110 and directed into the exhaust stack 164.

As discussed above, the controller 180 is communicatively coupled to themodulating gas valve 128 and the draft inducer blower 154 and isconfigured to adjust operation of the modulating gas valve 128 and/orthe draft inducer blower 154. In accordance with present techniques, thecontroller 180 of the modulating furnace 104 is further configured tocontrol operation of the various above-described components of themodulating furnace 104 in multiple, different operating modes. Forexample, the memory 184 may include instructions stored thereon that,when executed by the processor 182, cause the controller 180 to controloperation of the various components of the modulating furnace 104. Thecontroller 180 may be disposed inside a housing (e.g., enclosure 120) ofthe modulating furnace 104, may be disposed on a housing (e.g., on anexternal surface of the housing), or in another location separate fromthe modulating furnace 104. For example, the controller 180 may be thecontrol panel 82, another controller of the HVAC system 100, acontroller of the HVAC unit 12, a controller of the heating and coolingsystem 50, or other controller. In accordance with present embodiments,the controller 180 may be configured to execute a quick heat cyclealgorithm to determine whether, when, and how long to initiate a quickheat cycle mode of the modulating furnace 104. Based on thedetermination, the controller 180 may then execute the quick heat cyclemode accordingly.

For example, in the quick heat operating mode, the controller 180 maycontrol the modulating furnace 104 (e.g., the burner assembly 116, themodulating gas valve 128) to direct fuel 124 (e.g., gas) to the burners126 at an upper threshold (e.g., maximum) flow rate. In someembodiments, the controller 180 may control the burner assembly 116 tooperate at an upper threshold (e.g., maximum) firing rate of the burners126. Additionally or alternatively, during the quick heat operatingmode, the controller 190 may control the draft inducer blower 154 todraw the exhaust gas 160 through the heat exchanger 110 at an upperthreshold (e.g., maximum) flow rate at which the draft inducer blower154 is configured to designed to operate. In other words, in the quickheat operating mode, the controller 180 may control the modulatingfurnace 104 to operate at a full, 100 percent, upper threshold,predefined maximum, and/or maximum capacity (e.g., heat output, heattransfer rate, etc.)

The controller 180 may also be configured to operate the modulatingfurnace 104 in a modulating heat operating mode in which the controller180 controls the modulating furnace 104 (e.g., the burner assembly 116,the modulating gas valve 128) to supply a varying amount of fuel 124(e.g., gas). For example, in the modulating heat operating mode, thecontroller 180 may instruct the modulating gas valve 128 to supply fuel124 to the burners 126 based on feedback (e.g., sensor feedback). Insome embodiments, the controller 180 may receive feedback including aset point temperature in the interior space 119 (e.g., from athermostat) and a measured (e.g., current) temperature of the interiorspace 119 (e.g., from a sensor (e.g., interior space 119 sensor, returnair sensor, etc.). The controller 180 may determine a temperaturedifference between the set point temperature and the measuredtemperature and instruct the modulating gas valve 128 to supply fuel 124to the burners 126 based on the temperature difference. Additionally oralternatively, during the modulating heat operating mode, the controller190 may control the draft inducer blower 154 (e.g., based on thetemperature difference, sensor feedback, etc.) to operate at one or morespeeds to draw the exhaust gas 160 through the heat exchanger 110 at adesired (e.g., variable) flow rate. The controller 180 may control asetting of the modulating gas valve 128 and/or the draft inducer blower154 to correspond to the quick heat operating mode or the modulatingheat operating mode. For example, the controller 180 may control aposition of the modulating gas valve 128 to direct the above-describedupper threshold amount of fuel 124 (e.g., an amount of fuel 124 providedat a maximum rate) to the burners 126 in response to initiation of thequick heat operating mode. The controller 180 may also control theposition of the modulating gas valve 128 to direct a varying amount offuel 124 to the burners 126 in response to initiation of the modulatingheat operating mode. The controller 180 may similarly control a speed ofthe draft inducer blower 154 based on initiation of the quick heatoperating mode and initiation of the modulating heat operating mode.

As previously described, the controller 180 may determine whether andwhen to initiate quick heat cycle operation based on a quick heatalgorithm executed by the controller 180 and/or by another controller(e.g., control panel 82, a thermostat, etc.). In some embodiments, thequick heat algorithm may consider or analyze characteristics orparameters of recent cycles of the modulating furnace 104. In accordancewith the present disclosure, the term “cycle” or “furnace cycle” mayrefer to a time period beginning when operation of the modulatingfurnace 104 is initiated in response to a call for heating and endingwhen the call for conditioning is satisfied (e.g., operation of themodulating furnace 104 is suspended). In accordance with the presentdisclosure, the term “elapsed time” may refer to a time period beginningwhen operation of the modulating furnace 104 is initiated in response toa call for heating.

FIG. 7 is a schematic illustration of an embodiment of a control system220 for the modulating furnace 104. It should be appreciated that thecontrol system 220 may also be implemented, in accordance with thepresent techniques, with other modulating conditioning (e.g., heating,cooling, dehumidification, etc.) systems as previously described. In theillustrated embodiment, the control assembly 220 includes the controller180, which includes the processor 182 (e.g., one or more processors,processing circuitry, etc.), the memory 184 (e.g., non-transitory,computer-readable media having processor-executable instructions storedthereon), and communication circuitry 186. The control system 220further includes a thermostat 222, which includes a user interface 224.For example, the thermostat 222 may be a thermostat of the interiorspace 119. It should be noted that the thermostat 222 may be awall-mounted device or a handheld device such as a smart phone or someother network-connected device. In general, the thermostat 222 may beconfigured to receive an input (e.g., via the user interface 224 of thethermostat 222, which may include buttons, a display, a graphic userinterface [GUI], or any combination thereof) that sets a desiredtemperature of the conditioned space, referred to in certain instancesas a set-point. Further, in some embodiments, the user interface 224 maybe a component separate from the thermostat 222. For example, the userinterface 224 may be a mobile device, a tablet, a computer, or otherapparatus configured to receive user input. In such embodiments, theuser interface 224 may be communicatively coupled to the thermostat 222,the controller 180, and/or other component of the HVAC system 100. Forexample, the controller 180 may be communicatively coupled with thethermostat 222 and configured to receive a call from the thermostat 222.For example, the user interface of the thermostat 222 may receive aninput indicative of operation of the modulating furnace 104 in the quickheat operating mode. The control system 220 also includes a sensor 226(e.g., one or more sensors), such as a temperature sensor disposedwithin the interior space 119, a return air sensor of the HVAC system100 (e.g., HVAC unit 12, heating and cooling system 50), and/or othersensors. The memory 184 may include instructions stored thereon that,when executed by the processor 182, cause the controller 180 to performvarious functions (e.g., execute a quick heat algorithm in accordancewith the present disclosure). The controller 180, the thermostat 222,the user interface 224, and/or the sensor 226 may be communicativelycoupled via a wired and/or wireless arrangement (e.g., via a networksystem 228, such as an Internet, Wi-Fi, or Bluetooth system). While thecontroller 180 is described as a component of the modulating furnace104, any suitable control circuitry may be utilized to control operationof the modulating furnace 104. For example, a mobile device, a personalcomputer, a smart device, a laptop, a tablet, or any other suitabledevice may be utilized to control operation of the modulating furnace104 and/or execute the quick heat algorithm, as described herein.

As previously described, the controller 180 may receive a call forconditioning (e.g., heating). For example, the controller 180 mayreceive the call for conditioning from the thermostat 222 (e.g., via theuser interface 224, which may include one or more buttons, displays,graphic user interfaces [GUIs], dials, touchscreens, or any combinationthereof) and/or from the control panel 82. In response to receiving thecall, the controller 180 may execute a quick heat algorithm to initiateoperation of the modulating furnace 104. In some instances and asdescribed further below, execution of the quick heat algorithm may causethe controller 180 to operate the modulating furnace 104 in the quickheat operating mode, in the manner previously described, for a thresholdtime period. If the call for conditioning is not satisfied prior toexpiration of the threshold time period, the controller 180 may thenoperate the modulating furnace 104 in the modulating heat operating modeuntil the call is satisfied. For example, the controller 180 may operatethe modulating furnace 104 in the modulating heat operating modesubsequent to expiration of the threshold time period. Additionally oralternatively, the controller 180 may include a timer (e.g., a clock)configured to count an elapsed time from the call (e.g., receiving thecall, initiating operation of the modulating furnace 104). In certainembodiments, the controller 180 may compare the elapsed time from thetimer to the threshold time period and/or may operate the modulatingfurnace 104 in the modulating heat operating mode subsequent toexpiration of the threshold time period. In some embodiments, the timermay count down from the threshold time period and the controller 180 mayoperate the modulating furnace 104 in the modulating heat operating modesubsequent to expiration of the threshold time period on the timer.

In the quick heat algorithm employed by the controller 180, eachpreviously satisfied call from the thermostat may be associated with acycle of the modulating furnace that was used to satisfy the call. Thequick heat algorithm employed to initiate operation of the modulatingfurnace 104 may be based at least in part on recent (e.g., previous)cycles of the modulating furnace 104, whether the recent cycles, whichsatisfied previous calls from the thermostat 222, employed quick heatcycle operation, an elapsed time of the current cycle, and comparing theelapsed time to a threshold time period. A modulating heat cycle refersto a cycle that was completed without initiating quick heat operation. Aquick heat cycle refers to a cycle that was completed only afterinitiation of quick heat cycle operation (e.g., quick heat cycles mayinclude quick heat cycle operation and then include modulating heatcycle operation to satisfy the call from the thermostat 222).

The quick heat algorithm may include a comparison of the number ofconsecutive recent cycles which are modulating heat cycles and athreshold number of cycles. Thus, the controller 180 may compare anumber of consecutive recent modulating heat cycles with a thresholdnumber of cycles. If the number of consecutive recent modulating heatcycles meets or exceeds the threshold number of cycles, the controller180 may initiate operation of the modulating furnace 104 in the quickheat operating mode. Likewise, if the number of consecutive recentmodulating heat cycles fails to meet or exceed the threshold number ofcycles, the controller 180 may initiate operation of the modulatingfurnace 104 in the modulating heat operating mode. For example, if thethreshold number of cycles is five cycles, the modulating furnace 104 iscontrolled to operate in the modulating heat operating mode for at mostfive consecutive heating cycles, then the modulating furnace 104 iscontrolled to operate in the quick heat operating mode for the nextcycle after the five consecutive modulating heat cycles.

Additionally, the controller 180 may also compare the elapsed timecompared to a threshold time period and the comparison may be employedvia the quick heat algorithm. The quick heat algorithm may include acomparison of the elapsed time for the current cycle and the thresholdtime period. Thus, if the elapsed time meets or exceeds the thresholdtime period, the controller 180 may operate the modulating furnace 104in the modulating heat operating mode. In certain embodiments, thecontroller 180 may continue to operate the modulating furnace 104 in thequick heat operating mode until either of the call from the thermostat222 is satisfied or the elapsed time meets or exceeds the threshold timeperiod.

In one embodiment, the thermostat 222 may call for a temperatureincrease (e.g., a difference between the desired temperature (e.g., settemperature) and a current temperature of the conditioned space) of acertain number of degrees (e.g., Fahrenheit, Celsius) in the enclosedspace serviced by the modulating furnace 104. The call may be in theform of a value indicative of a desired temperature differential, avalue indicative of a desired temperature, a first value indicative of adesired temperature and a second value indicative of a currenttemperature, or the like. The controller 180 may receive the call fromthe thermostat 222 and, in response to the call, execute the quick heatalgorithm to initiate operation of the modulating furnace for an elapsedtime (e.g., an amount of time during which quick heat cycle operation isemployed and after which modulating heat cycle operation is initiated ifthe call is not satisfied prior to the elapsed time meeting or exceedinga threshold time period). For example, if the threshold time period is 8minutes, the modulating furnace 104 is controlled to operate in thequick heat operating mode for at most 8 minutes, and if the call fromthe thermostat 222 is not satisfied by the quick heat operating modebefore or by the time the 8 minutes expire, then the modulating furnace104 is controlled to operate in the modulating heat operating mode untilthe call from the thermostat 222 is satisfied.

Additionally or alternatively, the user interface of the thermostat 222may receive an input indicative of setting and/or adjusting a thresholdnumber of consecutive modulating heat cycles and/or a threshold timeperiod to operate the modulating furnace 104 in the quick heat operatingmode. For example, the user interface may receive an input to increasethe threshold time period (e.g., up to 4 minutes, 6 minutes, 8 minutes,10 minutes, 15 minutes, and so forth) and/or may receive an input todecrease the threshold time period (e.g., to 10 minutes, 8 minutes, 4minutes, and so forth).

As mentioned above, the sensor 226 may be a temperature sensorconfigured to detect a temperature in the space (e.g., interior space119) being conditioned by the modulating furnace 104. In certainembodiments, the sensor 226 may detect a temperature of return air(e.g., received by the HVAC system 100). When the temperature detectedby the sensor 226 indicates that the call from the thermostat 222 issatisfied (e.g., a set point temperature is reached), the controller 180may suspend operation of the modulating furnace 104. That is, thecontroller 190 may control the modulating furnace 104 to end the cycle(e.g., until another call for heating is received by the controller180). Additionally or alternatively, the controller 180 may control themodulating furnace 104 in the modulating heat cycle based on feedback(e.g., indicative of the measured temperature of the conditioned space)from the sensor 226. In certain embodiments, the controller 180 maydetermine a temperature difference between the temperature of theconditioned space (e.g., interior space 119) monitored by the sensor 226and a set point temperature (e.g., input via the thermostat 222 and/orinterface 224). The controller 180 may operate the modulating furnace104 in the modulating heat cycle operation mode based on the temperaturedifference. For example, the controller 180 may adjust the modulatinggas valve 128 to control a flow rate of the fuel 124 supplied to theburners 126 of the modulating furnace 104 based on the temperaturedifference. In some embodiments, the controller 180 may adjust themodulating gas valve 128 to decrease the fuel 124 flow rate as thetemperature difference decreases (e.g., the temperature of the interiorspace 119 approaches the set point temperature). The controller 180 mayadjust the modulating gas valve 128 to increase the fuel 124 flow rateas the temperature difference increases (e.g., the temperature of theinterior space 119 diverges from the set point temperature). In themodulating heat cycle operation, the controller 180 may additionally oralternatively control the draft inducer blower 154 similarly.

The quick heat algorithm employs additional features described in detailbelow with reference to later drawings. However, in general, a result(e.g., output or outcome) of the quick heat algorithm may be at least inpart a function of the above-described elapsed time, threshold timeperiod, and a number of cycles from the last quick heat cycle. Theoutput or outcome includes initiation of the modulating furnace 104during which the controller 180 operates the modulating furnace 104 inthe quick heat operating mode and, if the call from the thermostat 222is not satisfied prior to the threshold time period expiring or lapsing,after which the controller 180 operates the modulating furnace 104 inthe modulating heat operating mode. These and other features aredescribed in detail below with reference to later drawings.

With the foregoing in mind, FIG. 8 is an embodiment of a process flowdiagram illustrating a process 230 of executing a quick heat algorithm.In the illustrated embodiment, the process 230 includes receiving (block232) a call for heating from a thermostat, such as the thermostat 222.The controller 180 may receive the call and may associate (block 234)the call with a quick heat cycle for the modulating furnace 104. Forexample, the call may be indicative of a user selection of a quick heatcycle via the user interface, such as user interface 224 of thethermostat 222. Accordingly, the controller 180 may associate the callwith the quick heat cycle. Additionally or alternatively, the controller180 may associate the call with the quick heat cycle based on acomparison between the number of consecutive modulating heat cycles anda threshold number of cycles, as described herein.

The illustrated process 230 also includes operating (block 236) themodulating furnace 104 in a quick heat operating mode. In certainembodiments, in response to receiving the call and/or associating thecall with the quick heat cycle, the controller 180 may initiateoperation of the modulating furnace 104. For example, the controller 180may operate the modulating furnace 104 in the quick heat operating mode,as described herein. In certain embodiments, the controller 180 mayadjust the modulating gas valve 128 to increase a fuel flow rate of afuel 124 to a threshold (e.g., maximum) flow rate during the quick heatoperating mode. Additionally or alternatively, the controller 180 mayadjust the draft inducer blower 154 to produce a threshold (e.g.,maximum) flow rate of combustion products (e.g., exhaust gas 160)through the heat exchanger 110.

The illustrated process 230 also includes determining (block 238) anelapsed time for the current heating cycle. For example, the elapsedtime may be a time period beginning when operation of the modulatingfurnace 104 is initiated in response to the thermostat call. Theillustrated process 230 also includes comparing (block 240) the elapsedtime to a threshold time period. The threshold time period may be storedin the memory 184 of the controller 180. The controller 180 maydetermine (block 242) whether the elapsed time falls below or meets orexceeds the threshold time period. For example, the controller 180 maydetermine the elapsed time is 2 minutes and the threshold time period is4 minutes. As such, the controller 180 may compare the elapsed time tothe threshold time period and determine the elapsed time falls below thethreshold time period (YES path of block 242). Accordingly, thecontroller 180 may continue to operate the modulating furnace 104 in thequick heat operating mode until the threshold time period expires (e.g.,the elapsed time meets or exceeds the threshold time period).

As another example, the elapsed time may be 6 minutes and the thresholdtime period may also be 6 minutes. As such, the controller 180 maycompare the elapsed time to the threshold time period and determine theelapsed time meets (or exceeds) the threshold time period (NO path ofblock 242). Accordingly, the controller 180 may operate (block 244) themodulating furnace 104 in the modulating heat operating mode, asdescribed herein. For example, the controller 180 may adjust operationof the modulating furnace 104 from the quick heat operating mode to themodulating heat operating mode subsequent to the expiration of thethreshold time period. In certain embodiments, the controller 180 mayadjust the modulating gas valve 128 to decrease the fuel flow rate fromthe threshold (e.g., maximum) flow rate to a lower flow rate.Additionally or alternatively, the controller 180 may adjust the draftinducer blower 154 to produce a flow rate of combustion products (e.g.,exhaust gas 160) through the heat exchanger 110 that is lower than thethreshold (e.g., maximum) flow rate.

FIG. 9 is a block diagram of a sequence 250 of cycles for the modulatingfurnace of FIG. 5 , in accordance with an embodiment of the presentdisclosure. The sequence 250 may include any number of cycles, such asfirst cycle 252, second cycle 254, N−1th cycle 256, and Nth cycle 258.In certain embodiments, N may be any number and may be a thresholdnumber of modulating heat cycles before the controller 180 operates themodulating furnace 104 in a quick heat operating mode. Any number ofcycles may occur between the illustrated second cycle 254 and the N−1thcycle 256. For example, N may be 7 cycles and the N−1th cycle 256 may bethe sixth cycle in the sequence 250. In certain embodiments, thecontroller 180 may monitor the sequence of cycles to determine a numberof consecutive modulating heat cycles. For example, the controller 180may receive a call from the thermostat 222 for each cycle 252, 254, 256,258. In some embodiments, the first cycle 252, the second cycle 254, andthe N−1th cycle 256 may be modulating heat cycles. For example, thecontroller 180 may operate the modulating furnace 104 in the modulatingheat operating mode for the first cycle 252, the second cycle 254, theN−1th cycle 256, and any number of cycles between the second cycle 254and the N−1th cycle. In certain embodiments, the controller 180 maycompare the number of consecutive modulating heat cycles with athreshold number of cycles. For example, the controller 180 may receivea call from the thermostat 222 for heating. In response to the call, thecontroller 180 may determine the number of consecutive modulating heatcycles from previous calls for heating. Additionally or alternatively,the controller 180 may determine the number of cycles from the currentcall for heating and a previous call during which the modulating furnace104 was operated in the quick heat operating mode.

The controller 180 may compare the number of consecutive modulating heatcycles to the threshold number of cycles and may operate the modulatingfurnace 104 in either a modulating heat operating mode or a quick heatoperating mode based on the comparison. For example, if the number ofconsecutive modulating heat cycles meets or exceeds the threshold numberof cycles, then the controller 180 may operate the modulating furnace104 in the quick heat operating mode in response to the call for heatingfrom the thermostat 222. As such, the Nth cycle 258 may be a quick heatcycle of the modulating furnace 104. Alternatively, if the number ofconsecutive modulating heat cycles falls below the threshold number ofcycles, then the controller 180 may operate the modulating furnace 104in the modulating heat operating mode in response to the call forheating from the thermostat 222. Accordingly, the Nth cycle 258 may be amodulating heat cycle of the modulating furnace 104.

With the foregoing in mind, FIG. 10 is an embodiment of a process flowdiagram illustrating a process 260 of executing the quick heatalgorithm. In the illustrated embodiment, the process 260 includesreceiving (block 262) a call for heating from a thermostat, such as thethermostat 222. In certain embodiments, the controller 180 may receivethe call via a communication interface with the thermostat 222. Theillustrated process 260 may also include determining (block 264) anumber of consecutive cycles between the call and a previous callassociated with a quick heat cycle for the modulating furnace 104. Incertain embodiments, the controller 180 may store informationcorresponding to any number of cycles in the memory 184. For example,the controller 180 may receive information from the memory 184 for up tothe last 20 cycles (e.g., the last 15 cycles, the last 10 cycles, thelast 5 cycles, and so forth). The controller 180 may determine a numberof completed consecutive cycles since the last quick heat cycle. Forexample, the controller 180 may determine five consecutive modulatingheat cycles have been completed since the last quick heat cycle.

The controller 180 may also compare (block 266) the number ofconsecutive modulating heat cycles with a threshold number of cycles, asdescribed herein. The illustrated process 260 may also includedetermining (block 268) whether the number of consecutive modulatingheat cycles falls below or meets or exceeds the threshold cycle amount.For example, the controller 180 may determine the number of consecutivemodulating heat cycles is 9 cycles and the threshold number ofconsecutive modulating heat cycles is 8 cycles. As such, the controller180 may compare the number of consecutive modulating heat cycles withthe threshold number of consecutive modulating heat cycles and determinethe number of consecutive modulating heat cycles exceeds the thresholdnumber of consecutive modulating heat cycles (NO path of block 268).Accordingly, the controller 180 may operate (block 270) the modulatingfurnace 104 in a quick heat operating mode. In certain embodiments, inresponse to receiving the call and/or determining the number ofconsecutive modulating heat cycles meets or exceeds the threshold cycleamount, the controller 180 may initiate operation of the modulatingfurnace 104. For example, the controller 180 may operate the modulatingfurnace 104 in the quick heat operating mode, as described herein. Incertain embodiments, the controller 180 may adjust the modulating gasvalve 128 to increase a fuel flow rate of a fuel 124 to a threshold(e.g., maximum) flow rate during the quick heat operating mode.Additionally or alternatively, the controller 180 may adjust the draftinducer blower 154 to produce a threshold (e.g., maximum) flow rate ofcombustion products (e.g., exhaust gas 160) through the heat exchanger110.

As another example, the controller 180 may determine the number ofconsecutive modulating heat cycles is 4 cycles and the threshold numberof consecutive modulating heat cycles is 6 cycles. As such, thecontroller 180 may compare the number of consecutive modulating heatcycles with the threshold number of consecutive modulating heat cyclesand determine the number of consecutive modulating heat cycles fallsbelow the threshold number of consecutive modulating heat cycles (YESpath of block 268). Accordingly, the controller 180 may operate (block272) the modulating furnace 104 in the modulating heat operating mode,as described herein. For example, the controller 180 may initiateoperation of the modulating furnace 104 in the modulating heat operatingmode. In certain embodiments, the controller 180 may adjust themodulating gas valve 128 to decrease the fuel flow rate from thethreshold (e.g., maximum) flow rate to a lower flow rate. Additionallyor alternatively, the controller 180 may adjust the draft inducer blower154 to produce a flow rate of combustion products (e.g., exhaust gas160) through the heat exchanger 110 that is lower than the threshold(e.g., maximum) flow rate.

The present disclosure may provide one or more technical effects usefulin the operation of an HVAC system. For example, the disclosed controlsscheme employing the disclosed quick heat algorithm may improveefficiency of a modulating heat exchanger and a timeliness ofconditioning an environment (e.g., enclosed space) via the modulatingheat exchanger.

While only certain features and embodiments of the disclosure have beenillustrated and described, many modifications and changes may occur tothose skilled in the art, such as variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, including temperatures and pressures, mounting arrangements,use of materials, colors, orientations, and so forth without materiallydeparting from the novel teachings and advantages of the subject matterrecited in the claims. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeembodiments. It is, therefore, to be understood that the appended claimsare intended to cover all such modifications and changes as fall withinthe true spirit of the disclosure. Furthermore, in an effort to providea concise description of the exemplary embodiments, all features of anactual implementation may not have been described, such as thoseunrelated to the presently contemplated best mode of carrying out thedisclosure, or those unrelated to enabling the claimed disclosure. Itshould be noted that in the development of any such actualimplementation, as in any engineering or design project, numerousimplementation specific decisions may be made. Such a development effortmight be complex and time consuming, but would nevertheless be a routineundertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure, without undueexperimentation.

The techniques presented and claimed herein are referenced and appliedto material objects and concrete examples of a practical nature thatdemonstrably improve the present technical field and, as such, are notabstract, intangible or purely theoretical. Further, if any claimsappended to the end of this specification contain one or more elementsdesignated as “means for [perform]ing [a function] . . . ” or “step for[perform]ing [a function] . . . ”, it is intended that such elements areto be interpreted under 35 U.S.C. 112(f). However, for any claimscontaining elements designated in any other manner, it is intended thatsuch elements are not to be interpreted under 35 U.S.C. 112(f).

1. A controller of a modulating furnace of a heating, ventilation, and air conditioning (HVAC) system, the controller comprising a tangible, non-transitory, computer-readable medium having computer-executable instructions stored thereon that, when executed, are configured to cause processing circuitry to: receive a call for heating; associate the call for heating with a quick heat cycle; operate the modulating furnace in a quick heat operating mode for a threshold time period in response to the call for heating being associated with the quick heat cycle; and operate the modulating furnace in a modulating heat operating mode subsequent to expiration of the threshold time period.
 2. The controller of claim 1, wherein the computer-executable instructions, when executed, are configured to cause the processing circuitry to operate the modulating furnace in the modulating heat operating mode based on comparison of a set point temperature of a conditioned space and feedback indicative of a temperature of the conditioned space.
 3. The controller of claim 2, wherein the feedback indicative of the temperature of the conditioned space comprises a return air temperature.
 4. The controller of claim 1, wherein the computer-executable instructions, when executed, are configured to cause the processing circuitry to: determine a number of heating cycles executed by the modulating furnace between the call for heating and a previous call for heating; compare the number of heating cycles to a threshold number of heating cycles; and associate the call for heating with the quick heat cycle in response to the number of heating cycles meeting or exceeding the threshold number of heating cycles.
 5. The controller of claim 1, wherein the computer-executable instructions, when executed, are configured to cause the processing circuitry to operate the modulating furnace at a full capacity in the quick heat operating mode.
 6. The controller of claim 1, wherein the computer-executable instructions, when executed, are configured to cause the processing circuitry to associate the call for heating with the quick heat cycle in response to a user selection of a quick heat mode via a user interface.
 7. The controller of claim 1, wherein the computer-executable instructions, when executed, are configured to cause the processing circuitry to operate the modulating furnace in the modulating heat operating mode for a set time period subsequent to the expiration of the threshold time period.
 8. A heating, ventilation, and air conditioning (HVAC) system, comprising: a modulating furnace; and control circuitry configured to receive a call for heating associated with a quick heat cycle and, in response to the call for heating: operate the modulating furnace in a quick heat operating mode for a threshold time period; and subsequent to the threshold time period, operate the modulating furnace in a modulating heat operating mode.
 9. The HVAC system of claim 8, wherein the call for heating is associated with the quick heat cycle based on the control circuitry receiving a user input indicative of a selection of a quick heat mode.
 10. The HVAC system of claim 8, wherein the control circuitry is configured to associate the call for heating with the quick heat cycle based on a number of previous heating cycles executed since a previous call for heating associated with the quick heat cycle meeting or exceeding a threshold number of cycles.
 11. The HVAC system of claim 8, wherein the control circuitry is configured to operate the modulating furnace in the modulating heat operating mode based on comparison of a set point temperature of a conditioned space and feedback indicative of a temperature of the conditioned space.
 12. The HVAC system of claim 8, wherein the control circuitry is configured to operate the modulating furnace at one hundred percent capacity in the quick heat operating mode.
 13. The HVAC system of claim 12, wherein the control circuitry is configured to suspend operation of the modulating furnace based on the temperature of the conditioned space meeting or exceeding the set point temperature of the conditioned space.
 14. The HVAC system of claim 8, wherein the modulating furnace comprises: a burner configured to receive fuel and generate combustion products; and a modulating gas valve configured to control a flow rate of the fuel directed to the burner.
 15. The HVAC system of claim 14, wherein the control circuitry is configured to adjust the modulating gas valve to increase the flow rate of fuel during operation of the modulating furnace to an upper threshold rate in the quick heat operating mode.
 16. A heating, ventilation, and air conditioning (HVAC) system, comprising: a modulating furnace; and processing circuitry configured to receive a call for heating from a thermostat and, in response to the call for heating, execute a quick heat algorithm to: determine a number of heating cycles between the call for heating and a previous call for heating associated with a quick heat cycle; compare the number of heating cycles to a threshold number of cycles; in response to the number of heating cycles meeting or exceeding the threshold number of cycles, operate the modulating furnace in a quick heat operating mode; and in response to the number of heating cycles being below the threshold number of cycles, operate the modulating furnace in a modulating heat operating mode.
 17. The HVAC system of claim 16, wherein, in response to the number of heating cycles meeting or exceeding the threshold number of cycles, the processing circuitry is configured to: determine an elapsed time from receiving the call for heating; compare the elapsed time to a threshold time period; and operate the modulating furnace in the modulating heat operating mode in response to expiration of the threshold time period.
 18. The HVAC system of claim 16, wherein the modulating furnace comprises: heat exchange tubes configured to receive a heat exchange fluid; and a blower configured to control a flow rate of the heat exchange fluid through the heat exchange tubes.
 19. The HVAC system of claim 18, wherein, in the quick heat operating mode, the processing circuitry is configured to operate the blower to increase the flow rate of the heat exchange fluid to an upper threshold flow rate.
 20. The HVAC system of claim 16, wherein, in the quick heat operating mode, the processing circuitry is configured to operate the modulating furnace at a full capacity or a predefined maximum heating capacity. 